The trimerization of ethylene to produce 1-hexene constitutes a commercially significant process for the selective preparation of this alpha olefin, which in turn is useful for preparing a range of polyolefins, usually as a comonomer with ethylene. One widely employed ethylene trimerization catalyst system comprises a chromium carboxylate, a pyrrole compound, and a metal alkyl. For example, one ethylene trimerization catalyst system comprises a tris(2-ethylhexanoate) chromium(III), 2,5-dimethylpyrrole, triethylaluminum, and diethylaluminum chloride.
Typically, any method of preparing an active catalyst system can present challenges with respect to the chromium carboxylate utilized in the ethylene trimerization catalyst system. Batch-to-batch variations in the quality of commercial chromium(III) 2-ethylhexanoate, and the attendant inconsistency in catalytic system performance, have can have significant impacts upon the ethylene trimerization catalyst system productivity and selectivity. Therefore, it would be useful to discover and develop new catalyst systems, new methods for preparing the catalyst systems, and new methods for using the catalyst systems for preparing a trimerization product that might provide greater efficiency and cost effectiveness. In one aspect, new catalyst systems and methods for preparing the catalyst systems are needed that might reduce the amount of expensive activators in a catalyst system, or that might lower the cost or increase the efficiency of preparing chromium compounds used in the catalyst system.